1. Field of the Invention
The present invention relates to drywall finish trim devices typically utilized in finishing a drywall installation at a corner or terminus.
2. Description of the Prior Art
Drywall, sometimes also referred to as wallboard, is a staple in the construction industry as an economical alternative to joint compound for forming the interior walls and ceilings of rooms in residential, commercial, and industrial buildings. The materials used in drywall construction include gypsum board, plywood, fibre-and-pulp boards, and asbestos-cement boards. The large, rigid sheets are fastened directly to the frame of a building with nails, screws, or adhesives, or are mounted on furring (strips of wood nailed over the studs, joists, rafters, or masonry, which allow free circulation of air behind the interior wall). A significant advantage afforded by drywall construction is that it allows a builder to avoid the unnecessary delays attendant to the drying of wet plaster before other work can be started or before the on-site work required to achieve specific finishes may be completed. Wallboard is manufactured in both finished and unfinished forms, and finished wallboards may be faced with vinyl or other materials in a variety of permanent colors and textures so that they do not need to be painted when installed.
When employing drywall in construction, builders can easily cut the panels to any desired shape and size. However, workmen face a challenge in finishing drywall panels at an edge or corner. It is very difficult, if not impossible, to cut the edges of such panels with the precision, straightness, and smoothness that is required so that the abutted edges of adjoining panels form a straight corner that will afford an aesthetic finish. Additionally, cutting of the drywall panels exposes the soft, raw cores thereof, thus requiring some sort of covering to provide a finished appearance.
As a result, to cover drywall panel edges and enhance the aesthetics of a drywall joint, several devices and techniques may be employed in an effort to produce a structurally sound corner that will exhibit a smooth and seamless intersection. Devices proposed to achieve this result include drywall tape, trim and corner beads. When conventional drywall tape is used, it is applied to the joints and edges of abutting panels and is covered with wet joint compound that is feathered and smoothed to cover the newly created seams. When the joint compound has dried, the tape and drywall can be sanded, painted, covered, or otherwise finished in whatever manner is desired. A great deal of skill is required, however, to apply and form the joint compound to create a sufficiently straight intersection that will not exhibit, when taped and sanded to a finish, evidence of scuffing and tearing in the body of the tape.
In light of the limitations of drywall tape, trim strips or corner beads are often utilized in effort to produce a seamless and aesthetically pleasing edge trim or intersection at the corners of drywall panels.
Such trim may take many different forms such as a flat strip, a corner bead having flanges diverging at any one of a number of different angles, or a J strip to cap the edge of a dry wall panel. For the purposes of this invention, the particular angular configuration is not critical, but use in conjunction with numerous different configurations presently in existence and that may be developed in the future is contemplated. Further examples of corner trims include beads with perpendicular flanges, corner trims with a rib formed at the juncture of the flanges, flanges angled at 135xc2x0 to one another, those configured with somewhat of a Z shape, those with soft line corners, and those with offsets or other configurations traditionally used in the trade and known to those skilled in the art.
To enhance the finished appearance of construction finished drywall with such trim, efforts have been made to cover a hard structural core with an exterior covering of paper or paper-like material to enhance the finished appearance. It is recognized that by covering a plastic or metal core with paper, the paper will serve to cooperate with the covering on adjacent drywall panels to, when covered with a joint compound, afford a continuous smooth appearance from such panels and over the resultant trimmed joint. The compound may be sanded down and feathered in effort to provide a continuous smooth surface.
A disadvantage arising from the use of such paper covered trim cores is that, during the sanding process, the workman sometimes sands through such compound and into the paper layer. This sanding tends to scuff up the fiber in the paper layer leaving somewhat of a scuffed or abraded surface, oftentimes with frayed fiber ends. This results in a discontinuous and unattractive surface. Efforts to solve this problem have led to the development of various different trims and corner beads that incorporate a protective layer constructed of either a strengthening compound or paper impregnated at the outer surface.
While these advancements may act to provide some strengthening to the covering paper, they do not adequately address the problem raised by sanding through the layer of material treated by the strengthening compound or the problems posed by separation of the paper from the core element with shrinkage of the paper cover. This issue becomes especially evident when trim strips or beads are subjected to high temperatures above about 100xc2x0 F., as during storage in sheds, during transportation, or after prolonged exposure to various environmental conditions. In such instances, the paper covering will often shrink and bubble up on the core or pull away from it, particularly in any areas of any irregularity such as adjacent any shoulder or rib formed in such core. This bubbling and separation of the paper covering is often detected only at the construction site after the product has been transported and stored for preparation of the drywall phase of the construction project. Consequently, the onsite workman must oftentimes reject and discard any strips with such deteriorated trim resulting in significant waste of both product and time.
Consequently, there exists a need for a durable, affordable, and aesthetically pleasing corner bead device having a paper covering not susceptible to shrinkage or rupturing at elevated temperatures or after prolonged exposure to the environment.
The present invention provides for an improved drywall trim that resists surface cracking, bubbling, or rupturing and separation of the covering strip from the core element even at elevated temperatures. It is characterized by a protective core covering, preferably in the form of a stock paper covering strip that has been, while shrunk, bonded to the core. It is also contemplated that the cover strip may take the form of any durable fibrous covering strip that is well suited for use in such drywall construction applications. This covering strip may be specially manufactured for the present application, or may take the form of a commercially available material having the moisture evaporated therefrom to achieve a dehydrated shrunken state. The key requirement for the purposes of the present invention is that the material must be pre-shrunk and adhered to the core element in its pre-shrunk state.
During the manufacturing process, the covering paper or other suitable material defining the covering strip is pre-shrunk as by heating to an elevated temperature and maintained in that state as it is adhered to the core element of the bead. This heating may be accomplished by a variety of means, such as ovens or dryers, that are well known to those in the industry. The paper, in such a heated and pre-shrunk state, may then be mated to a metal or other suitable core material by using a hot melt glue or other appropriate bonding means. Then, when the trim device is cooled and rehydrated from atmospheric conditions, any tendency for such covering to expand relative to the core will result in relatively uniform application of expansive stress to such cover and the bond line. Then when such paper covering strip is subsequently exposed to high temperatures or dry conditions leading to dehydration and consequent shrinkage, the body of the covering will tend to shrink back from its expanded condition to a neutral condition and then to a contracted condition as it dehydrates below the dehydrated state it had at the time of bonding. This then results in application of much less stress to the bond line between such cover and the core than would be the case for a similar paper cover that had not been pre-shrunk.
The trim of the present invention can be made by selecting a fibrous covering strip, preferably in the form of a stock paper. The covering strip may be separately heated to dehydrate and shrink it. It may then be bonded in such a heated state by a layer of appropriate adhesive. Thusly configured, overhanging portions of the paper covering strip may be folded around and under the respectively covered edges of the core element, and/or the trim may be finished by forming it into a suitable shape for the desired application and cutting appropriately dimensioned segments therefrom.
Other objects and features of the invention will become apparent from consideration of the following description taken in conjunction with the accompanying drawing.